I have reached the point where I fear that I may seriously damage my car and I would greatly appreciate the help of the many people on here I know understand this system much better than I. I will provide a fair amount of detail on the situation as this is a rather complicated problem, and my extensive searching has led to a huge number of possibilities. If your in a hurry just skip to the numbered points and I will fill in the blanks.
Problem: Transitional (1-3 shakes of the ping can) audible pings at 3500RPM, becoming more frequent.
History: 2003 wrx, 40K original owner miles, regular services all completed on schedule. 93 octane for 3 months then downgraded to only 91 octane available in KS for 2 years, occasional ambiguously audible pings. Spoke to dealer but they just said yeah, that is detonation. Lots of 15 minute trips. Moved to NC, complete 30K service at dealer, 93 octane gas. No pings. 3500 feet elevation, very steep grades and long descents. Flash Cobb stage 1 93 octane last fall, no pings until a warm snap in January. Suspect bad gas, start shopping around. Can't find good gas here, get audible pings on unpredictable and infrequent occasions. Seems like every time I get good gas off the mountain no pings (still in NC but chevron or sunoco instead of BP or Exxon). Just enough to make me decide to flash to 91 octane map, but went for stage II instead.
Installed uppipe (coated) and catted DP, stock turbo heat shield, flashed 93octane Cobb stage II map. Pings under heavy load, somewhat sporadic. Flash 91 stage II map, running 93 octane, cleaned temperature bulb but not MAF (one speck of dust on bulb, MAF spotless; stock air filters all the way) and reset ECU. One 2-3 shakes of the can ping under load when heat soaked, takes a pretty solid run with extended uphill 2nd & 3rd gear push.
Change PCV, no excessive oil in intercooler (no drips just a smudge when inverted for 60 minutes. Return condenser pipes along intercooler have droplet at end, small build up at throttle body hose, throttle body looks fairly clean. Go in search of Sunoco one county away, closed when I get there & mom & pop store, so I fill with exxon and add synpower injector cleaner. Ten miles of downhill from there, engine breaking in 4th for extended periods, then get moderate uphill ping, & pings on level (not heat soaked). Ping now consistent, not going away.
Purchase air filter, spark plugs, install 104 octane booster from store. Thats where she sits.
Results from searches:
1)Cobb map is conservative, runs rich. Should be trusted.
or (take your pick on the thread)
Cobb map is actually leaner than stock - never heard of anyone running Cali 91 map on 93 octane, but is a possibility.
2) PCV valve - should be changed every 15K miles, or never (take your pick). Mine was fine.
2.a) Oil catch can - not done.
3) Turbo oil seals shot - seems not. No oil in downpipe, not much in intercooler
4) Engine deposits - can cause preignition as well, or increase compression and otherwise cause spark knock (at issue here). Finishing 1st tank with synpower cleaner.
5) Spark plugs - do show signs of detonation (metal balls stuck to ceter electrode). Plugs replaced with OEM gapped to .028 (yesterday, not tested hard yet).
6) Blow by - oil in intake, reduces octane. Check compression.
7) Elevation - Colorado people say 91 octane = 93 octane there, should be a safeguard
Need higher octane at high elevation (web auto professionals and occasional threads)
8) Boost - peaks at 15.8 settles at 15 then tapers. Compensation map in ECU reduces peak boost by 1 PSI per ~3500' IIRC, so normal stage II numbers.
9) Vacuum issues (haven't figured out how to check system yet).
10) Injectors plugged, tired, or imbalanced (40K miles, always top tier gas, never cleaned). Unlikely - all four cylinders are affected.
11) MAF or Temp sensor problem.
12) Dealer - go parade my just installed stage II setup and void my warranty on a totally unabused motor with a potentially bad ring land. Get unheard of and unreported "ping" reflash that was never mentioned when I was there complaining about ping.
13) Knock Sensor? Don't know how to test that.
14) Head gasket??? I guess I should add this because I have had to burp the coolant a few times recently. I had a small coolant leak from a line a while back but it was supposedly corrected/pressure tested at the dealer. The system was then flushed at 30K (dealer) and there has never been any indication of overheating.
OK, so without throwing on a huge number of guages and replacing every bolt on part of my car, how should I proceed? I don't want to just get it tuned at boxer4racing and have an underlying problem even if it solves the issue. I don't want to leave anything on the table if I go to that expense, and I don't want an issue later. I could remove the green bracket of death and send the injectors out. I could do seafoam, or auto RX or whatever that stuff is. As of now my warranty should be intact if I remove my stage II setup I just installed.
PLEASE PLEASE give me some advise!!